Electrode structure and light-emitting device using the same

ABSTRACT

An electrode structure includes at least two first electrodes and at least two second electrodes configured to be electrically connected in parallel to a power supply. Each of the first electrodes includes at least one first pad and at least one first extending wire with one end connected to the first pad, and the at least two first electrodes are spaced apart from each other. Each of the second electrodes includes at least one second pad and at least one second extending wire with one end connected to the second pad, and the at least two second electrodes are spaced apart from each other.

BACKGROUND OF THE INVENTION

(A) Field of the Invention

The present invention relates to an electrode structure andlight-emitting devices using the same, and more particularly, to anelectrode structure with parallel-connected electrodes configured toprevent the light-emitting device from overheating by eliminating thecurrent-crowding phenomenon so as to dramatically improve thereliability of the light-emitting device.

(B) Description of the Related Art

Semiconductor light-emitting devices such as light-emitting diodes (LED)are widely used in traffic lights, vehicle electronics, LCD backinglights, and general illumination. In the light-emitting diode an n-typesemiconductor layer, a light-emitting region and a p-type semiconductorlayer are essentially made to grow on a substrate to form a layeredstructure, and the electrodes are formed on the p-type semiconductorlayer and on the n-type semiconductor layer. Light is generated throughthe recombination of holes and electrons that have been injected throughthe semiconductor layers to the light-emitting region, and then emittedthrough a light transmitting electrode on the p-type semiconductor layeror from the substrate. The material used for preparing the visiblelight-emitting diode includes the III-V compound such as AlGaInP forgreen, yellow, orange or red light-emitting diodes, and GaN for blue orultraviolet light-emitting diodes, wherein the GaN light-emitting diodeis formed on the sapphire substrate.

FIG. 1 illustrates a top view of a nitride light-emitting device 30according to the prior art, and FIG. 2 illustrates a cross-sectionalview of the nitride light-emitting device 30 according to the prior art.The nitride light-emitting device 30 according to the prior art includesa sapphire substrate 32, an n-type nitride semiconductor layer 34, alight-emitting layer 36, a p-type nitride semiconductor layer 38, acontact layer 40, a p-type electrode 42, and an n-type electrode 44. Then-type electrode 44 is formed on the top surface of the n-type nitridesemiconductor layer 34, and the p-type electrode 42 is formed on the topsurface of the contact layer 44.

The nitride light-emitting device 30 suffers from a current-crowingproblem, i.e., the current is not distributed uniformly between then-type electrode 44 and the p-type electrode 42, and concentrates at alocal region 46 of the light-emitting layer 36 in close proximity to then-type electrode 44. This current-crowding problem not only increasesthe forward biasing voltage of the light-emitting diode, but alsoreduces the light-emitting efficiency of the light-emitting layer 36 atthe side distant from the n-type electrode 44, which decreases theoverall brightness of the light-emitting device 30. In addition,progressively accumulating heat in the local region 46 causes theoverheating phenomenon, which dramatically decreases the reliability ofthe light-emitting diode.

FIG. 3 and FIG. 4 illustrate a light-emitting diode array disclosed inUS 2005/0224822. The preparation of the light-emitting diode arrayincludes forming a depression by etching, filling dielectric material 17into the depression to divide the light-emitting stack consisting of afirst type semiconductor 14, a light-emitting layer 15 and a second typesemiconductor layer 16 into a plurality of light-emitting diodes 1 a and1 b, and connecting the first electrode 18 and the second electrode 19of the adjacent light-emitting diodes 1 a and 1 b in series to form theseries-connected light-emitting diode array, as shown in FIG. 4.

SUMMARY OF THE INVENTION

One aspect of the present invention provides an electrode structure withparallel-connected electrodes configured to prevent the light-emittingdevice from overheating by eliminating the current-crowding phenomenonso as to dramatically improve the reliability of the light-emittingdevice.

An electrode structure according to this aspect of the present inventionincludes at least two first electrodes and at least two secondelectrodes configured to be electrically connected in parallel to apower supply. Each of the first electrodes includes at least one firstpad and at least one first extending wire with one end connected to thefirst pad, and the at least two first electrodes are spaced apart fromeach other. Each of the second electrodes includes at least one secondpad and at least one second extending wire with one end connected to thesecond pad, and the at least two second electrodes being spaced apartfrom each other.

Another aspect of the present invention provides a light-emitting deviceincluding a substrate; a stacked structure including a first typesemiconductor layer positioned on the substrate, a light-emittingstructure positioned on the first type semiconductor layer, and a secondtype semiconductor layer positioned on the light-emitting structure,wherein the stacked structure includes a depression exposing the firsttype semiconductor layer; at least two first electrodes positioned onthe first type semiconductor layer in the depression, each of the firstelectrodes including at least one first pad and at least one firstextending wire with one end connected to the first pad, the at least twofirst electrodes being spaced apart from each other; and at least twosecond electrodes positioned on the second type semiconductor layer,each of the second electrodes including at least one second pad and atleast one second extending wire with one end connected to the secondpad, the at least two second electrodes being spaced apart from eachother.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe same purposes of the present invention. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The objectives and advantages of the present invention will becomeapparent upon reading the following description and upon reference tothe accompanying drawings in which:

FIG. 1 illustrates a top view of a nitride light-emitting deviceaccording to the prior art;

FIG. 2 illustrates a cross-sectional view of the nitride light-emittingdevice according to the prior art;

FIG. 3 and FIG. 4 illustrate a light-emitting diode array disclosed inUS 2005/0224822;

FIG. 5 is a top view of the light-emitting device according to oneembodiment of the present disclosure;

FIG. 6 is a cross-sectional view along the line 1-1 in FIG. 5;

FIG. 7 is an equivalent circuit of the light-emitting device in FIG. 5electrically connected to a power supply;

FIG. 8 is a top view of the light-emitting device according to oneembodiment of the present disclosure;

FIG. 9 is a cross-sectional view along the line 2-2 in FIG. 8;

FIG. 10 is an equivalent circuit of the light-emitting device in FIG. 8electrically connected to a power supply;

FIG. 11 is a top view of the light-emitting device according to oneembodiment of the present disclosure;

FIG. 12 is a cross-sectional view along the line 3-3 in FIG. 11;

FIG. 13 is an equivalent circuit of the light-emitting device in FIG. 11electrically connected to a power supply;

FIG. 14 is a top view of the light-emitting device according to oneembodiment of the present disclosure;

FIG. 15 is a cross-sectional view along the line 4-4 in FIG. 14;

FIG. 16 is an equivalent circuit of the light-emitting device in FIG. 14electrically connected to a power supply;

FIG. 17 is a top view of the light-emitting device according to oneembodiment of the present disclosure;

FIG. 18 is a cross-sectional view along the line 5-5 in FIG. 17;

FIG. 19 is an equivalent circuit of the light-emitting device in FIG. 17electrically connected to a power supply;

FIG. 20 is a top view of the light-emitting device according to oneembodiment of the present disclosure;

FIG. 21 is a cross-sectional view along the line 6-6 in FIG. 20;

FIG. 22 is an equivalent circuit of the light-emitting device in FIG. 20electrically connected to a power supply; and

FIG. 23 illustrates the experimental relation between the brightness(Φe) and the distance between the first extending wires according to oneembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 5 to 7 illustrate a light-emitting device 50 according to oneembodiment of the present disclosure, wherein FIG. 5 is a top view ofthe light-emitting device 50, FIG. 6 is a cross-sectional view along theline 1-1 in FIG. 5, and FIG. 7 is an equivalent circuit of thelight-emitting device 50 electrically connected to a power supply 92.Referring to FIG. 5 and FIG. 6, the light-emitting device 50 includes asubstrate 52, a stacked structure 62 with a depression 64 therein, atleast two first electrodes 70 positioned in the depression 64, and atleast two second electrodes 80 positioned on the stacked structure 62.The stacked structure 62 includes a first type (n-type) semiconductorlayer 54 positioned on the substrate 52, a light-emitting structure 56positioned on the first type semiconductor layer 54, a second type(p-type) semiconductor layer 58 positioned on the light-emittingstructure 56, and a contact layer 60 positioned on the second typesemiconductor layer 58.

The at least two first electrodes 70 serve as the n-type electrode ofthe light-emitting device 50 and the at least two second electrodes 80serve as the p-type electrode of the light-emitting device 50 to form anelectrode structure 90. The depression 64 exposes the first typesemiconductor layer 54, and the at least two first electrodes 70 arepositioned on the first type semiconductor layer 54 in the depression64. The at least two first electrodes 70 are spaced apart from eachother, and each of the first electrodes 70 includes at least one firstpad 72 and at least one first extending wire 74 with one end connectedto the first pad 72. The at least two second electrodes 80 are spacedapart from each other and positioned on the second type semiconductorlayer 58 such as on the surface of the contact layer 60. Each of thesecond electrodes 80 includes at least one second pad 82 and at leastone second extending wire 84 with one end connected to the second pad82. The light-emitting device 50 is rectangular, and the first pad 72 ispositioned at a corner 66.

Referring to FIG. 5, the first electrode 70 includes a plurality offirst branches 76 with one end connected to the first extending wire 74,and the second electrode 80 includes a plurality of second branches 86with one end connected to the second extending wire 84. The secondelectrode 80 is positioned in the first electrode 70. The secondextending wire 84 is straight and positioned in the interior of thelight-emitting device 50, and the first extending wire 74 is straightand positioned at the border of the light-emitting device 50. In oneembodiment of the present disclosure, the distance between the secondpad 82 and the border of the electrode structure 90 (or the border ofthe light-emitting device 50) is less than 200 microns.

Referring to FIG. 5 and FIG. 7, the light-emitting device 50 can beconsidered as two light-emitting diodes 50A and 50B that use the samestacked structure 62 but use the respective p-type electrode 80 andn-type electrode 70. In case of connecting the first pad 72 of the firsttype electrode (n-type electrode) 70 to the negative electrode of thepower supply 92 and connecting the second pad 82 of the second electrode(p-type electrode) 80 to the positive electrode of the power supply 92,the light-emitting device 50 can be considered as the two light-emittingdiodes 50A and 50B connecting to the power supply 92 in parallel. Atleast one end of the depression 64 is inside the interior of the stackedstructure 92, and the depression 64 in the light-emitting device 50A andthe depression in the light-emitting device 50B are arranged in amirror-image manner. In addition, the first electrode 70 and the secondelectrode 80 in the light-emitting device 50A and those in thelight-emitting device 50B are arranged in a mirror-image manner.

The design of the p-type electrode 42 and the n-type electrode 44 in thenitride light-emitting device 30 shown in FIG. 1 and FIG. 2 onlyprovides a single current path, and the current is not distributeduniformly, thus generating the current-crowding problem. Thecurrent-crowding problem not only increases the forward biasing voltageof the light-emitting diode, but also decreases the light-emittingefficiency of the light-emitting layer 36 at the side distant from then-type electrode 44, which decreases the overall brightness of thelight-emitting device 30. Furthermore, heat accumulating progressivelyin the local region 46 causes the overheating phenomenon, whichdramatically decreases the reliability of the light-emitting diode. Incontrast, the electrode structure 90 of the present disclosure uses themultiple electrode design to provide multiple current paths so as tosolve the current-crowding problem of the prior art and reduce theforward biasing voltage, and the overheating problem is eliminated.

The light-emitting diode array shown in FIG. 3 and FIG. 4 electricallyconnects the adjacent light-emitting diodes 1 a and 1 b in series bywires 20 to form the series-connected light-emitting diode array. Theoverall resistance of the series-connected light-emitting diode array ishigher than that of the individual light-emitting diode, and theseries-connected light-emitting diode array needs a greater powersupply. In contrast, the electrode structure 90 of the presentdisclosure uses the multiple electrode design such that thelight-emitting device 50 can be considered as two light-emitting diodes50A and 50B connected to the power supply 92 in parallel, the overallresistance of the parallel-connected light-emitting diodes is lower thanthat of the individual light-emitting diode, and thus the light-emittingdevice requires a lesser power supply.

FIGS. 8 to 10 illustrate a light-emitting device 150 according toanother embodiment of the present disclosure, wherein FIG. 8 is a topview of the light-emitting device 150, FIG. 9 is a cross-sectional viewalong the line 2-2 in FIG. 8, and FIG. 10 is an equivalent circuit ofthe light-emitting device 150 electrically connected to a power supply192. Referring to FIG. 9 and FIG. 10, the light-emitting device 150includes a substrate 152, a stacked structure 162 with a depression 164therein, at least two second electrodes 180 positioned in the depression164, and at least two first electrodes 170 positioned on the stackedstructure 162. The stacked structure 162 includes a first type (n-type)semiconductor layer 154 positioned on the substrate 152, alight-emitting structure 156 positioned on the first type semiconductorlayer 154, a second type (p-type) semiconductor layer 158 positioned onthe light-emitting structure 156, and a contact layer 160 positioned onthe second type semiconductor layer 158.

The at least two first electrodes 170 serve as the p-type electrode ofthe light-emitting device 150 and the at least two second electrodes 180serve as the n-type electrode of the light-emitting device 150 to forman electrode structure 190. The at least two first electrodes 170 arepositioned on the second type semiconductor layer 158 such as on thesurface of the contact layer 160, and the at least two first electrodes170 are spaced apart from each other. Each of the first electrodes 170includes at least one first pad 172 and at least one first extendingwire 174 with one end connected to the first pad 172. The light-emittingdevice 150 is rectangular, and the first pad 172 is positioned at acorner 166. The depression 164 exposes the first type semiconductorlayer 154, and the at least two second electrodes 180 are positioned onthe first type semiconductor layer 154 in the depression 164. The atleast two second electrodes 180 are spaced apart from each other, andeach of the second electrodes 180 includes at least one second pad 182and at least one second extending wire 184 with one end connected to thesecond pad 182.

Referring to FIG. 8, the first electrode 170 includes a plurality offirst branches 176 with one end connected to the first extending wire174, and the second electrode 180 includes a plurality of secondbranches 186 with one end connected to the second extending wire 184.The second electrode 180 is positioned in the first electrode 170. Thesecond extending wire 184 is straight and positioned in the interior ofthe light-emitting device 150, and the first extending wire 174 isstraight and positioned at the border of the light-emitting device 150.In one embodiment of the present disclosure, the distance between thesecond pad 182 and the border of the electrode structure 190 (or theborder of the light-emitting device 150) is less than 200 microns.

Referring to FIG. 8 and FIG. 10, the light-emitting device 150 can beconsidered as two light-emitting diodes 150A and 150B that use the samestacked structure 162 but use the respective n-type electrode 180 andp-type electrode 170. In case of connecting the first pad 172 of thefirst type electrode 170 (p-type electrode) to the positive electrode ofthe power supply 192 and connecting the second pad 182 of the secondelectrode (n-type electrode) 180 to the negative electrode of the powersupply 192, the light-emitting device 150 can be considered as the twolight-emitting diodes 150A and 150B connecting to the power supply 192in parallel. At least one end of the depression 164 is inside theinterior of the stacked structure 192, and the depression 164 in thelight-emitting device 150A and that in the light-emitting device 150Bare arranged in a mirror-image manner. In addition, the first electrode170 and the second electrode 180 in the light-emitting device 150A andthose in the light-emitting device 150B are arranged in a mirror-imagemanner.

FIGS. 11 to 13 illustrate a light-emitting device 250 according toanother embodiment of the present disclosure, wherein FIG. 11 is a topview of the light-emitting device 250, FIG. 12 is a cross-sectional viewalong the line 3-3 in FIG. 11, and FIG. 13 is an equivalent circuit ofthe light-emitting device 250 electrically connected to a power supply292. The light-emitting device 250 includes a substrate 252, a stackedstructure 262 with a depression 264 therein, at least two firstelectrodes 270 positioned in the depression 264, and at least two secondelectrodes 280 positioned on the stacked structure 262. The stackedstructure 262 includes a first type (n-type) semiconductor layer 254positioned on the substrate 252, a light-emitting structure 256positioned on the first type semiconductor layer 254, a second type(p-type) semiconductor layer 258 positioned on the light-emittingstructure 256, and a contact layer 260 positioned on the second typesemiconductor layer 258.

The at least two first electrodes 270 serve as the n-type electrode ofthe light-emitting device 250 and the at least two second electrodes 280serve as the p-type electrode of the light-emitting device 250 to forman electrode structure 290. The depression 264 exposes the first typesemiconductor layer 254, and the at least two first electrodes 270 arepositioned on the first type semiconductor layer 254 in the depression264. The at least two first electrodes 270 are spaced apart from eachother, and each of the first electrodes 270 includes at least one firstpad 272 and at least one first extending wire 274 with one end connectedto the first pad 272. The at least two second electrodes 280 are spacedapart from each other and positioned on the second type semiconductorlayer 258 such as on the surface of the contact layer 260. Each of thesecond electrodes 280 includes at least one second pad 282 and at leastone second extending wire 284 with one end connected to the second pad282. The light-emitting device 250 is rectangular, and the first pad 272is positioned at a corner 266.

Referring to FIG. 11, the first electrode 270 includes a plurality offirst branches 276 with one end connected to the first extending wire274, and the second electrode 280 includes a plurality of secondbranches 286 with one end connected to the second extending wire 284.The second electrode 280 is positioned in the first electrode 270. Thesecond extending wire 284 can be straight or arched, and positioned inthe interior of the light-emitting device 250. In addition, the firstextending wire 274 is straight and positioned at the border of thelight-emitting device 150, or arched and positioned in the interior ofthe light-emitting device 250. In one embodiment of the presentdisclosure, the distance between the second pad 282 and the border ofthe electrode structure 290 (or the border of the light-emitting device250) is less than 200 microns.

Referring to FIGS. 11 and 13, the light-emitting device 250 can beconsidered as two light-emitting diodes 250A and 250B that use the samestacked structure 262 but use the respective p-type electrode 280 andn-type electrode 270. In case of connecting the first pad 272 of thefirst type electrode (n-type electrode) 270 to the negative electrode ofthe power supply 292 and connecting the second pad 282 of the secondelectrode (p-type electrode) 280 to the positive electrode of the powersupply 292, the light-emitting device 250 can be considered as the twolight-emitting diodes 250A and 250B connecting to the power supply 292in parallel. At least one end of the depression 264 is inside theinterior of the stacked structure 292, and the depression 264 in thelight-emitting device 250A and that in the light-emitting device 250Bare arranged in a mirror-image manner. In addition, the first electrode270 and the second electrode 280 in the light-emitting device 250A andthose in the light-emitting device 250B are arranged in a mirror-imagemanner.

FIGS. 14 to 16 illustrate a light-emitting device 350 according to oneembodiment of the present disclosure, wherein FIG. 14 is a top view ofthe light-emitting device 350, FIG. 15 is a cross-sectional view alongthe line 4-4 in FIG. 14, and FIG. 16 is an equivalent circuit of thelight-emitting device 350 electrically connected to a power supply 392.Referring to FIG. 14 and FIG. 15, the light-emitting device 350 includesa substrate 352, a stacked structure 362 with a depression 364 therein,at least two second electrodes 380 positioned in the depression 364, andat least two first electrodes 370 positioned on the stacked structure362. The stacked structure 362 includes a first type (n-type)semiconductor layer 354 positioned on the substrate 352, alight-emitting structure 356 positioned on the first type semiconductorlayer 354, a second type (p-type) semiconductor layer 358 positioned onthe light-emitting structure 356, and a contact layer 360 positioned onthe second type semiconductor layer 358.

The at least two second electrodes 380 serve as the n-type electrode ofthe light-emitting device 350 and the at least two first electrodes 370serve as the p-type electrode of the light-emitting device 350 to forman electrode structure 390. The at least two first electrodes 370 arespaced apart from each other and positioned on the second typesemiconductor layer 358 such as on the surface of the contact layer 360.Each of the first electrodes 370 includes at least one first pad 372 andat least one first extending wire 374 with one end connected to thefirst pad 372. The light-emitting device 350 is rectangular, and thefirst pad 372 is positioned at a corner 366. The depression 364 exposesthe first type semiconductor layer 354, and the at least two secondelectrodes 380 are positioned on the first type semiconductor layer 354in the depression 364. The at least two second electrodes 380 are spacedapart from each other, and each of the second electrodes 380 includes atleast one second pad 382 and at least one second extending wire 384 withone end connected to the second pad 382.

Referring to FIG. 14, the first electrode 370 includes a plurality offirst branches 376 with one end connected to the first extending wire374, and the second electrode 380 includes a plurality of secondbranches 386 with one end connected to the second extending wire 384.The second electrode 380 is positioned in the first electrode 370. Thesecond extending wire 384 is straight or arched, and positioned in theinterior of the light-emitting device 350, and the first extending wire374 is straight or arched, and positioned at the border of thelight-emitting device 350. In one embodiment of the present disclosure,the distance between the second pad 382 and the border of the electrodestructure 390 (or the border of the light-emitting device 350) is lessthan 200 microns.

Referring to FIGS. 14 and 16, the light-emitting device 350 can beconsidered as two light-emitting diodes 350A and 350B that use the samestacked structure 362 but use the respective n-type electrode 380 andp-type electrode 370. In case of connecting the first pad 372 of thefirst type electrode (p-type electrode) 370 to the positive electrode ofthe power supply 392 and connecting the second pad 382 of the secondelectrode (n-type electrode) 380 to the negative electrode of the powersupply 392, the light-emitting device 350 can be considered as the twolight-emitting diodes 350A and 350B connecting to the power supply 392in parallel. At least one end of the depression 364 is inside theinterior of the stacked structure 392, and the depression 364 in thelight-emitting device 350A and that in the light-emitting device 350Bare arranged in a mirror-image manner. In addition, the first electrode370 and the second electrode 380 in the light-emitting device 350A andthose in the light-emitting device 350B are arranged in a mirror-imagemanner.

FIGS. 17 to 19 illustrate a light-emitting device 450 according to oneembodiment of the present disclosure, wherein FIG. 17 is a top view ofthe light-emitting device 450, FIG. 18 is a cross-sectional view alongthe line 5-5 in FIG. 17, and FIG. 19 is an equivalent circuit of thelight-emitting device 450 electrically connected to a power supply 492.Referring to FIG. 17 and FIG. 18, the light-emitting device 450 includesa substrate 452, a stacked structure 462 with a depression 464 therein,at least two second electrodes 480 positioned in the depression 464, andat least two first electrodes 470 positioned on the stacked structure462. The stacked structure 462 includes a first type (n-type)semiconductor layer 454 positioned on the substrate 452, alight-emitting structure 456 positioned on the first type semiconductorlayer 454, a second type (p-type) semiconductor layer 458 positioned onthe light-emitting structure 456, and a contact layer 460 positioned onthe second type semiconductor layer 458.

The at least two second electrodes 480 serve as the n-type electrode ofthe light-emitting device 450 and the at least two first electrodes 470serve as the p-type electrode of the light-emitting device 450 to forman electrode structure 490. The at least two first electrodes 470 arespaced apart from each other and positioned on the second typesemiconductor layer 458 such as on the surface of the contact layer 460.The first electrodes 470 can be an interdigital electrode including atleast one first pad 472 and at least one first extending wire 474 withone end connected to the first pad 472. For example, the first electrode470 can be an interdigital electrode including two first extending wires474. The depression 464 exposes the first type semiconductor layer 454,and the at least two first electrodes 470 are positioned on the firsttype semiconductor layer 454 in the depression 464. The at least twosecond electrodes 480 are spaced apart from each other, and each of thesecond electrode 480 includes at least one second pad 482 and at leastone second extending wire 484 with one end connected to the second pad482. For example, the second electrode 480 can be an interdigitalelectrode including three second extending wires 484. In one embodimentof the present disclosure, the distance between the second pad 482 andthe border of the electrode structure 490 (or the border of thelight-emitting device 450) is less than 200 microns.

Referring to FIG. 17 and FIG. 19, the light-emitting device 450 can beconsidered as two light-emitting diodes 450A and 450B that use the samestacked structure 462 but use the respective p-type electrode 480 andn-type electrode 470. In case of connecting the first pad 472 of thefirst type electrode (p-type electrode) 470 to the positive electrode ofthe power supply 492 and connecting the second pad 482 of the secondelectrode (n-type electrode) 480 to the negative electrode of the powersupply 492, the light-emitting device 450 can be considered as the twolight-emitting diodes 450A and 450B connecting to the power supply 492in parallel. At least one end of the depression 464 is inside theinterior of the stacked structure 492, and the depression 464 in thelight-emitting device 450A and that in the light-emitting device 450Bare arranged in a mirror-image manner.

The light-emitting device 450 is rectangular, the first pad 472 ispositioned at a corner 466, and the second pad 482 is positioned aroundthe middle of a side 468 opposite to the corner 466. In addition, thefirst electrode 470 and the second electrode 480 in the light-emittingdevice 450A and those in the light-emitting device 450B are arranged ina mirror-image manner. The first pad 472 and the second pad 482 arepositioned in opposite corners in the light-emitting device 450A, andthe first pad 472 and the second pad 482 are positioned in oppositecorners in the light-emitting device 450B.

FIGS. 20 to 22 illustrate a light-emitting device 550 according to oneembodiment of the present disclosure, wherein FIG. 20 is a top view ofthe light-emitting device 550, FIG. 21 is a cross-sectional view alongthe line 6-6 in FIG. 20, and FIG. 22 is an equivalent circuit of thelight-emitting device 350 electrically connected to a power supply 592.Referring to FIG. 20 and FIG. 21, the light-emitting device 550 includesa substrate 552, a stacked structure 562 with a depression 564 therein,at least two first electrodes 570 positioned in the depression 564, andat least two second electrodes 580 positioned on the stacked structure562. The stacked structure 562 includes a first type (n-type)semiconductor layer 554 positioned on the substrate 552, alight-emitting structure 556 positioned on the first type semiconductorlayer 554, a second type (p-type) semiconductor layer 558 positioned onthe light-emitting structure 556, and a contact layer 560 positioned onthe second type semiconductor layer 558.

The at least two first electrodes 570 serve as the n-type electrode ofthe light-emitting device 550 and the at least two second electrodes 580serve as the p-type electrode of the light-emitting device 550 to forman electrode structure 590. The depression 564 exposes the first typesemiconductor layer 554, the at least two first electrodes 570 arepositioned on the first type semiconductor layer 554 in the depression564, and the at least two first electrodes 570 are spaced apart fromeach other. Each of the first electrodes 570 can be an interdigitalelectrode including at least one first pad 572 and at least one firstextending wire 574 with one end connected to the first pad 572. Forexample, the first electrode 570 can be an interdigital electrodeincluding two first extending wires 574. The first extending wire 574 ispositioned in the interior of the light-emitting device 550, and doesnot surround the border of the light-emitting device 550.

The at least two second electrodes 580 are spaced apart from each otherand positioned on the second type semiconductor layer 558 such as on thesurface of the contact layer 560. Each of the second electrodes 580includes at least one second pad 582 and at least one second extendingwire 584 with one end connected to the second pad 582. For example, thesecond electrode 580 can be an interdigital electrode including threesecond extending wires 584. The first extending wire 574 is positionedin the interior of the light-emitting device 550, and does not surroundthe border of the light-emitting device 550. In one embodiment of thepresent disclosure, the distance between the second pad 582 and theborder of the electrode structure 590 (or the border of thelight-emitting device 550) is less than 200 microns.

Referring to FIG. 20 and FIG. 22, the light-emitting device 550 can beconsidered as two light-emitting diodes 550A and 550B that use the samestacked structure 562 but use the respective p-type electrode 580 andn-type electrode 570. In case of connecting the first pad 572 of thefirst type electrode (n-type electrode) 570 to the negative electrode ofthe power supply 592 and connecting the second pad 582 of the secondelectrode (p-type electrode) 580 to the positive electrode of the powersupply 592, the light-emitting device 550 can be considered as the twolight-emitting diodes 550A and 550B connecting to the power supply 592in parallel. At least one end of the depression 564 is inside theinterior of the stacked structure 592, and the depression 564 in thelight-emitting device 550A and that in the light-emitting device 550Bare arranged in a mirror-image manner.

The distance between the first pad 572 and the second pad 582 is greaterthan 70% of the width of the light-emitting device 550. Preferably, thedistance between the first pad 572 and the second pad 582 is less than120% of the width of the light-emitting device 550. The distance betweenthe first extending wire 574 and the second extending wire 582 isbetween 5% and 15% of the width of the light-emitting device 550. Thefirst electrode 572 and the second electrode 582 occupy an area between5% and 10% of that of the light-emitting device 550. The first extendingwire 572 is not parallel to the border of the light-emitting device 550,the second extending wire 582 is not parallel to the border of thelight-emitting device 550, and the first extending wire 572 is notparallel to the second extending wire 582.

The light-emitting device 550 is rectangular, the first pad 572 ispositioned at a corner 566, and the second pad 582 is positioned aroundthe middle of a side 568 opposite to the corner 566. In addition, thefirst electrode 570 and the second electrode 580 in the light-emittingdevice 550A and those in the light-emitting device 550B are arranged ina mirror-image manner. The first pad 572 and the second pad 582 arepositioned in opposite corners in the light-emitting device 550A, andthe first pad 572 and the second pad 582 positioned in opposite cornersin the light-emitting device 550B.

FIG. 23 illustrates the experimental relation between the brightness(Φe) and the distance between the first extending wire and the secondextending wire, which applies to the embodiments shown in FIGS. 5 to 22.It can be seen in FIG. 23 that the maximum brightness is located at thedistance about 140 microns, and the width of the light-emitting deviceis about 1150 micron, i.e., the distance between the first extendingwire and the second extending wire is about 12% of the width of thelight-emitting device. In one embodiment of the present disclosure, thedistance between the first extending wire and the second extending wireis between 5% and 15% of the width of the light-emitting device, thedistance between the first pad and the second pad is greater than 70% ofthe width of the light-emitting device. Preferably, the distance betweenthe first pad and the second pad is less than 120% of the width of thelight-emitting device. In one embodiment of the present disclosure, thefirst electrode and the second electrode occupy an area between 5% and10% of that of the light-emitting device. In one embodiment of thepresent disclosure, the first extending wire is not parallel to theborder of the light-emitting device, the second extending wire is notparallel to the border of the light-emitting device, and the firstextending wire is not parallel to the second extending wire.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made thereto without departing from the spirit andscope of the invention as defined by the appended claims. For example,many of the processes discussed above can be implemented in differentmethodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. An electrode structure, comprising: firstelectrodes physically separated from each other, each of the firstelectrodes comprising a first pad and a first extending wire connectedto the first pad, wherein the first pads of the first electrodes areseparated from each other having a first distance therebetween; andsecond electrodes substantially surrounded by the first electrodes, eachof the second electrodes comprising a second pad and a second extendingwire connected to the second pad, the second electrodes being physicallyseparated from one another, the second pads of the second electrodes areseparated from each other having a second distance therebetween, whereinthe second distance is shorter than the first distance, wherein thesecond electrode comprises a plurality of second branches connected tothe second extending wire.
 2. The electrode structure of claim 1,wherein the first electrodes and the second electrodes are electricallyconnected in parallel.
 3. The electrode structure of claim 1, whereinthe electrode structure has a border which is away from the second padby a distance less than 200 microns.
 4. The electrode structure of claim1, wherein the first extending wire, the second extending wire, or bothare cured or straight.
 5. The electrode structure of claim 1, whereinthe first pad is positioned at a corner of the electrode structure. 6.The electrode structure of claim 1, wherein the first extending wire hasa portion not parallel to the second extending wire.
 7. The electrodestructure of claim 1, wherein the first extending wire is parallel tothe second extending wire.